fix up CONTRIBUTING.rst
fix up CONTRIBUTING.rst

Get rid of the openstack boilerplate and indicate that we are accepting PRs
and issues on githhub.

Closes #1

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>

ivuk/pylxd,lxc/pylxd,Saviq/pylxd,lxc/pylxd,javacruft/pylxd